A commonly used technique for ventillating hospital patients, involves the application of low pressure pulses to the airway of a patient, with each pressure pulse causing expansion of the patient's lung to force him to breathe at a typical normal rate such as 16 breaths per minute. This mechanical breathing approach has many disadvantages which are recognized in the field.
A more recently developed technique, commonly referred to as high frequency jet ventillation, involves the application of small volume air pulses (oxygen may be added) to the patient's lung, at a frequency much higher than typical breathing rates, such as above 100 pulses per minute. The air pulses bring oxygen to the alveoli of the lungs without necessitating expansion and contraction of the patient's lungs. While this technique has great promise, the equipment for applying the air pulses has not been highly efficient. One simple approach is to utilize a valve in series with a hospital air supply (typically about 50 psi) and to use an oscillator to turn the valve on and off. Such a high frequency air pulse source is unsatisfactory because of the danger that the valve will stick open, and because it is very difficult to accurately control the volume of air applied to the patient. Another technnique involves the use of a motor driven piston pump which pumps a controlled amount of air at every cycle. However, the air pulses are not of an efficient configuration, and the moving parts of the apparatus increase its cost and maintenance requirements. A high frequency medical breathing apparatus which was of simple construction, which could be easily and safely powered in a hospital environment, and which produced air pulses of high efficiency, would be of considerable value in the furtherance of high frequency ventilation techniques.